I played 1 years ago and to make leathers u had to put the tunning liquid after put the 4 limed skins, so they will become all 4 leathers.
I did yesterday the same thing, but only one became leather and the others 3 are at 99,9%. i added 10L of tunning and only one of 3 became leather.
There is a way to transform all 4 the lime skins into leathers with only 10L?